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Regulatory (Narrative) (Detail) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Annual accrual, storm damage reserve $ 8.0  
Storm damage reserve 47.6 43.6
Tampa Electric Co [Member]
    
Annual accrual, storm damage reserve 8.0  
Storm damage reserve $ 47.6 $ 43.6